Up to this time, wooden materials have been used for producing columns and beams and braces. These wooden components are framed together to form a building skeleton. However, in order to improve the strength, stability, and durability of the components, use of steel materials has also been considered. Applicant of this application proposed a composite beam which is formed of a steel material and a wooden material (Japanese patent laid open TOKUKAIHEI 8-13690). This composite beam is illustrated by the perspective views shown in FIG. 1a and FIG. 1b. As shown in these figures, this composite beam is formed of a steel beam (3) and a wooden member (4). The cross section of the steel beam is I-shaped. Namely, a pair of flat plate members (1) are lined in parallel and are connected each other by a perpendicular plate member (2) at the central position of the flat plate members (1). On the outer surfaces of the flat plate members (1), wooden members (4) are attached. Under this configuration, the strength, stability, and durability of the component is increased due to the use of the steel beam member (3), and the application of conventional wood-working processing to the beam becomes possible due to the attachment of the wooden members (4).
In the above-described composite beam structure, there are provided two bolts (5) for connecting the column (6) to the beam, protruding upward from the upper surface of the wooden member (4). In order to connect the columns with the beam member (3), the two bolts (5) are inserted into two holes among four holes formed at the bottom of the column (6). In addition, an H-shaped metal bracket (7) is attached across the wooden member (4) and the column (6). In order to secure the joint between the two components, the metal bracket (7) is firmly fixed to the composite beam by driving nails (8) into the wooden member (4) and the column (6) on both sides of the wooden member (4) and the column (6).
According to the above described conventional joined structure of the composite beam and column as shown in FIGS. 1a and 1b, however, one must drive the nails (8) through the bracket (7) to join the two members, making it time-consuming and labor-intensive. Also, in order for a construction worker to work efficiently, four holes need to be created at the four corners of the square bottom surface of the column (6) so that he/she does not need to find whether the column (6) is positioned in a right direction in which the two bolts (5) can be inserted into the bottom holes of the column (6). This increases the labor for processing the column (6). In addition, because the bracket (7) is fixed across the sides of the wooden member (4) and the column (6) and therefore is exposed, it is inevitable that the attached bracket (7) contacts with other surrounding components such as the metal fittings or furring strips, causing excess time and labor during construction works of the building skeleton.
In general, in one aspect, the present invention is a joint structure for joining a composite beam and a column. The composite beam comprises an I-beam and a pair of wooden members, each attached to one of two opposing flat plate members of the I-beam. The joint structure further comprises a mortise pin provided on the composite beam and protruding beyond a outer surface of one of the wooden members, which mortise pin is provided with a through-hole at a predetermined position therein, a bottom hole provided at a bottom surface of the column, which bottom hole is adapted to receive the mortise pin, and a horizontal hole provided at a side face of the column at a position corresponding to the through-hole of the mortise pin. The composite beam is connected to the column by inserting the mortise pin into the bottom hole of the column and inserting a locking pin into the through-hole of the mortise pin and the horizontal hole of the column such that the joint of the composite beam and the column is firmly secured.
In general, in another aspect, the present invention is a method of joining a composite beam and a column, which composite beam comprises an I-beam and a pair of wooden members, each attached to one of two opposing flat plate members of the I-beam. The method comprises providing a mortise pin on the composite beam such that the mortise pin protrudes beyond a outer surface of one of the wooden members, which mortise pin is provided with a through-hole at a predetermined position therein, providing a bottom hole at a bottom surface of the column, which bottom hole is adapted to receive the mortise pin, providing a horizontal hole at a side face of the column at a position corresponding to the through-hole of the mortise pin, connecting the composite beam with the column by inserting the mortise pin into the bottom hole of the column, and inserting a locking pin into the through-hole of the mortise pin and the horizontal hole of the column such that joint of the composite beam and the column is firmly secured.